## Appendix A: Candidate members of Lupus I

As we explain in Sect. 2, we proposed 43 objects to be observed with X-shooter. Twelve out of these 43 objects were observed during a filler program, and in this work we fully characterized

them. The rest of our targets in this sample that were not observed are listed in Table A.1. Among these targets, only 2MASS J15464664-3210006 (Eisner et al. 2007) is partly characterized, and 20 objects are identified as candidate YSOs using Gaia DR2 (Zari et al. 2018).

<table><caption>**Table A.1.** Astrometric properties of the candidate Lupus I members that were not observed by X-shooter, with their errors in parentheses.</caption><thead><tr><th>Name</th><th>α (J2000)<br>(h:m:s)</th><th>δ (J2000)<br>(d:m:s)</th><th>ω<br>(mas)</th><th>μ<sub>α*</sub><br>(mas/yr)</th><th>μ<sub>δ</sub><br>(mas/yr)</th><th>J<br>(mag)</th></tr></thead><tbody><tr><td>2MASS J15464664-3210006<sup>a</sup></td><td>15 46 46.64</td><td>-32 10 00.62</td><td>7.05(0.021)</td><td>-19.47(0.023)</td><td>-23.76(0.014)</td><td>11.22</td></tr><tr><td>Gaia DR2 6013000844869745664</td><td>15 39 24.47</td><td>-35 58 50.88</td><td>6.62(0.039)</td><td>-18.00(0.081)</td><td>-22.23(0.057)</td><td>10.11</td></tr><tr><td>Gaia DR2 6013065853493820416<sup>b</sup></td><td>15 43 15.62</td><td>-35 39 38.18</td><td>6.88(0.015)</td><td>-17.68(0.018)</td><td>-24.51(0.012)</td><td>10.20</td></tr><tr><td>Gaia DR2 6011737574730221568<sup>c</sup></td><td>15 50 46.50</td><td>-34 22 38.49</td><td>6.69(0.019)</td><td>-16.20(0.020)</td><td>-22.52(0.015)</td><td>10.74</td></tr><tr><td>Gaia DR2 6012258330925877632<sup>d</sup></td><td>15 53 36.13</td><td>-33 31 02.60</td><td>6.92(0.016)</td><td>-16.97(0.018)</td><td>-24.57(0.016)</td><td>10.75</td></tr><tr><td>Gaia DR2 6039383622075982848<sup>e</sup></td><td>15 57 09.76</td><td>-32 04 33.91</td><td>6.72(0.02)</td><td>-14.24(0.023)</td><td>-23.58(0.015)</td><td>10.56</td></tr><tr><td>Gaia DR2 6011518462675791872<sup>f</sup></td><td>15 48 13.16</td><td>-35 43 31.08</td><td>6.62(0.023)</td><td>-16.65(0.028)</td><td>-24.31(0.023)</td><td>11.48</td></tr><tr><td>Gaia DR2 6011797738632729216<sup>g</sup></td><td>15 57 20.96</td><td>-35 00 01.21</td><td>6.71(0.027)</td><td>-16.29(0.033)</td><td>-24.21(0.024)</td><td>11.65</td></tr><tr><td>Gaia DR2 6014049985115937408</td><td>15 34 59.21</td><td>-34 58 16.16</td><td>6.83(0.097)</td><td>-17.76(0.16)</td><td>-24.03(0.11)</td><td>12.16</td></tr><tr><td>Gaia DR2 6014830844535625344<sup>h</sup></td><td>15 47 58.08</td><td>-33 46 59.53</td><td>6.84(0.027)</td><td>-17.73(0.031)</td><td>-24.48(0.025)</td><td>11.31</td></tr><tr><td>Gaia DR2 6014224051546189568</td><td>15 34 42.05</td><td>-34 17 48.09</td><td>6.66(0.098)</td><td>-17.36(0.134)</td><td>-23.67(0.094)</td><td>11.94</td></tr><tr><td>Gaia DR2 6009936093645659136</td><td>15 43 49.43</td><td>-36 48 38.64</td><td>6.94(0.13)</td><td>-20.45(0.28)</td><td>-22.89(0.19)</td><td>10.92</td></tr><tr><td>Gaia DR2 6039633559115225344<sup>i</sup></td><td>15 52 59.02</td><td>-31 38 33.57</td><td>6.59(0.03)</td><td>-18.34(0.036)</td><td>-22.89(0.029)</td><td>11.93</td></tr><tr><td>Gaia DR2 6013187040287810944<sup>j</sup></td><td>15 37 53.31</td><td>-35 55 12.42</td><td>6.74(0.027)</td><td>-17.9(0.03)</td><td>-24.08(0.024)</td><td>11.95</td></tr><tr><td>Gaia DR2 6016139332082870272</td><td>15 39 25.88</td><td>-32 10 04.68</td><td>6.42(0.40)</td><td>-20.32(0.54)</td><td>-23.65(0.37)</td><td>10.81</td></tr><tr><td>Gaia DR2 6013126738951338624<sup>k</sup></td><td>15 43 28.48</td><td>-35 17 27.40</td><td>6.77(0.032)</td><td>-17.67(0.035)</td><td>-24.48(0.022)</td><td>11.91</td></tr><tr><td>Gaia DR2 6013190201383772288</td><td>15 37 53.00</td><td>-35 52 28.70</td><td>6.75(0.055)</td><td>-19.08(0.13)</td><td>-22.62(0.087)</td><td>12.22</td></tr><tr><td>Gaia DR2 6013077192207599232<sup>m</sup></td><td>15 43 11.42</td><td>-35 26 34.43</td><td>6.78(0.032)</td><td>-17.32(0.034)</td><td>-24.29(0.025)</td><td>11.82</td></tr><tr><td>Gaia DR2 6015181897983193728<sup>m</sup></td><td>15 51 57.84</td><td>-33 29 33.17</td><td>6.74(0.032)</td><td>-16.22(0.039)</td><td>-22.37(0.026)</td><td>12.03</td></tr><tr><td>Gaia DR2 6014590429442468096<sup>m</sup></td><td>15 45 06.91</td><td>-35 06 21.73</td><td>6.99(0.036)</td><td>-16.97(0.042)</td><td>-23.09(0.029)</td><td>11.82</td></tr><tr><td>Gaia DR2 6009995742152335232<sup>m</sup></td><td>15 44 26.97</td><td>-36 25 42.75</td><td>6.52(0.034)</td><td>-18.30(0.043)</td><td>-23.21(0.031)</td><td>11.82</td></tr><tr><td>Gaia DR2 6011607694917034112<sup>m</sup></td><td>15 50 00.76</td><td>-35 29 19.71</td><td>7.23(0.044)</td><td>-20.18(0.052)</td><td>-25.32(0.034)</td><td>12.37</td></tr><tr><td>Gaia DR2 6011695690208264320<sup>m</sup></td><td>15 47 59.03</td><td>-34 56 38.36</td><td>6.99(0.06)</td><td>-17.93(0.069)</td><td>-25.07(0.045)</td><td>12.69</td></tr><tr><td>Gaia DR2 6011261726715424128</td><td>15 50 29.19</td><td>-36 25 11.80</td><td>6.92(0.11)</td><td>-17.08(0.23)</td><td>-23.52(0.16)</td><td>13.32</td></tr><tr><td>Gaia DR2 6015222957871475584</td><td>15 48 46.12</td><td>-33 18 35.48</td><td>6.69(0.13)</td><td>-19.21(0.26)</td><td>-23.77(0.17)</td><td>13.77</td></tr><tr><td>Gaia DR2 6013030875279571328</td><td>15 41 55.22</td><td>-35 59 35.36</td><td>6.97(0.12)</td><td>-17.12(0.24)</td><td>-25.52(0.14)</td><td>13.17</td></tr><tr><td>Gaia DR2 6014112107523072640<sup>m</sup></td><td>15 34 35.79</td><td>-34 36 01.54</td><td>6.88(0.084)</td><td>-16.89(0.087)</td><td>-24.841(0.066)</td><td>13.14</td></tr><tr><td>Gaia DR2 6012977136650130560<sup>m</sup></td><td>15 39 48.47</td><td>-36 13 48.07</td><td>6.94(0.10)</td><td>-20.069(0.11)</td><td>-23.61(0.069)</td><td>12.81</td></tr><tr><td>Gaia DR2 6015141830223216640</td><td>15 50 19.17</td><td>-33 50 07.12</td><td>6.84(0.15)</td><td>-17.29(0.29)</td><td>-26.46(0.19)</td><td>13.92</td></tr><tr><td>Gaia DR2 6011581856393988352<sup>n</sup></td><td>15 48 06.26</td><td>-35 15 48.15</td><td>6.05(0.07)</td><td>-12.22(0.084)</td><td>-21.04(0.057)</td><td>10.56</td></tr><tr><td>Gaia DR2 6016191485871670400</td><td>15 38 35.63</td><td>-32 02 37.66</td><td>6.53(0.26)</td><td>-18.90(0.39)</td><td>-23.38(0.28)</td><td>14.35</td></tr></tbody></table>

<footnote><sup>a</sup> 2MASS J15464664-3210006 is an M2, T Tauri star (Eisner et al. 2007). <sup>b</sup> aka UCAC4 272-080482, this target is a YSO candidate (Zari et al. 2018). <sup>c</sup> aka UCAC4 279-083370, this target is a YSO candidate (Zari et al. 2018). <sup>d</sup> aka UCAC4 283-086052, this target is a YSO candidate (Zari et al. 2018). <sup>e</sup> aka RX J1557.1-3204A, this target is a YSO candidate (Zari et al. 2018). <sup>f</sup> aka UCAC4 272-081081, this target is a YSO candidate (Zari et al. 2018). <sup>g</sup> aka UCAC4 275-083957, this target is a YSO candidate (Zari et al. 2018). <sup>h</sup> aka UCAC4 282-082547, this target is a YSO candidate (Zari et al. 2018). <sup>i</sup> aka UCAC4 292-084899, this target is a YSO candidate (Zari et al. 2018). <sup>j</sup> aka UCAC4 271-080669, this target is a YSO candidate (Zari et al. 2018). <sup>k</sup> aka UCAC4 274-080590, this target is a YSO candidate (Zari et al. 2018). <sup>l</sup> aka UCAC4 274-080590, this target is a YSO candidate (Zari et al. 2018). <sup>m</sup> This target is a YSO candidate (Zari et al. 2018). <sup>n</sup> aka UCAC4 274-081081, this target is a YSO candidate (Zari et al. 2018).</footnote>
## Appendix A: Candidate members of Lupus I

As we explain in Sect. 2, we proposed 43 objects to be observed with X-shooter. Twelve out of these 43 objects were observed during a filler program, and in this work we fully characterized

them. The rest of our targets in this sample that were not observed are listed in Table A.1. Among these targets, only 2MASS J15464664-3210006 (Eisner et al. 2007) is partly characterized, and 20 objects are identified as candidate YSOs using Gaia DR2 (Zari et al. 2018).

<table><caption>**Table A.1.** Astrometric properties of the candidate Lupus I members that were not observed by X-shooter, with their errors in parentheses.</caption><thead><tr><th>Name</th><th>α (J2000)<br>(h:m:s)</th><th>δ (J2000)<br>(d:m:s)</th><th>ω<br>(mas)</th><th>μ<sub>α*</sub><br>(mas/yr)</th><th>μ<sub>δ</sub><br>(mas/yr)</th><th>J<br>(mag)</th></tr></thead><tbody><tr><td>2MASS J15464664-3210006<sup>a</sup></td><td>15 46 46.64</td><td>-32 10 00.62</td><td>7.05(0.021)</td><td>-19.47(0.023)</td><td>-23.76(0.014)</td><td>11.22</td></tr><tr><td>Gaia DR2 6013000844869745664</td><td>15 39 24.47</td><td>-35 58 50.88</td><td>6.62(0.039)</td><td>-18.00(0.081)</td><td>-22.23(0.057)</td><td>10.11</td></tr><tr><td>Gaia DR2 6013065853493820416<sup>b</sup></td><td>15 43 15.62</td><td>-35 39 38.18</td><td>6.88(0.015)</td><td>-17.68(0.018)</td><td>-24.51(0.012)</td><td>10.20</td></tr><tr><td>Gaia DR2 6011737574730221568<sup>c</sup></td><td>15 50 46.50</td><td>-34 22 38.49</td><td>6.69(0.019)</td><td>-16.20(0.020)</td><td>-22.52(0.015)</td><td>10.74</td></tr><tr><td>Gaia DR2 6012258330925877632<sup>d</sup></td><td>15 53 36.13</td><td>-33 31 02.60</td><td>6.92(0.016)</td><td>-16.97(0.018)</td><td>-24.57(0.016)</td><td>10.75</td></tr><tr><td>Gaia DR2 6039383622075982848<sup>e</sup></td><td>15 57 09.76</td><td>-32 04 33.91</td><td>6.72(0.02)</td><td>-14.24(0.023)</td><td>-23.58(0.015)</td><td>10.56</td></tr><tr><td>Gaia DR2 6011518462675791872<sup>f</sup></td><td>15 48 13.16</td><td>-35 43 31.08</td><td>6.62(0.023)</td><td>-16.65(0.028)</td><td>-24.31(0.023)</td><td>11.48</td></tr><tr><td>Gaia DR2 6011797738632729216<sup>g</sup></td><td>15 57 20.96</td><td>-35 00 01.21</td><td>6.71(0.027)</td><td>-16.29(0.033)</td><td>-24.21(0.024)</td><td>11.65</td></tr><tr><td>Gaia DR2 6014049985115937408</td><td>15 34 59.21</td><td>-34 58 16.16</td><td>6.83(0.097)</td><td>-17.76(0.16)</td><td>-24.03(0.11)</td><td>12.16</td></tr><tr><td>Gaia DR2 6014830844535625344<sup>h</sup></td><td>15 47 58.08</td><td>-33 46 59.53</td><td>6.84(0.027)</td><td>-17.73(0.031)</td><td>-24.48(0.025)</td><td>11.31</td></tr><tr><td>Gaia DR2 6014224051546189568</td><td>15 34 42.05</td><td>-34 17 48.09</td><td>6.66(0.098)</td><td>-17.36(0.134)</td><td>-23.67(0.094)</td><td>11.94</td></tr><tr><td>Gaia DR2 6009936093645659136</td><td>15 43 49.43</td><td>-36 48 38.64</td><td>6.94(0.13)</td><td>-20.45(0.28)</td><td>-22.89(0.19)</td><td>10.92</td></tr><tr><td>Gaia DR2 6039633559115225344<sup>i</sup></td><td>15 52 59.02</td><td>-31 38 33.57</td><td>6.59(0.03)</td><td>-18.34(0.036)</td><td>-22.89(0.029)</td><td>11.93</td></tr><tr><td>Gaia DR2 6013187040287810944<sup>j</sup></td><td>15 37 53.31</td><td>-35 55 12.42</td><td>6.74(0.027)</td><td>-17.9(0.03)</td><td>-24.08(0.024)</td><td>11.95</td></tr><tr><td>Gaia DR2 6016139332082870272</td><td>15 39 25.88</td><td>-32 10 04.68</td><td>6.42(0.40)</td><td>-20.32(0.54)</td><td>-23.65(0.37)</td><td>10.81</td></tr><tr><td>Gaia DR2 6013126738951338624<sup>k</sup></td><td>15 43 28.48</td><td>-35 17 27.40</td><td>6.77(0.032)</td><td>-17.67(0.035)</td><td>-24.48(0.022)</td><td>11.91</td></tr><tr><td>Gaia DR2 6013190201383772288</td><td>15 37 53.00</td><td>-35 52 28.70</td><td>6.75(0.055)</td><td>-19.08(0.13)</td><td>-22.62(0.087)</td><td>12.22</td></tr><tr><td>Gaia DR2 6013077192207599232<sup>m</sup></td><td>15 43 11.42</td><td>-35 26 34.43</td><td>6.78(0.032)</td><td>-17.32(0.034)</td><td>-24.29(0.025)</td><td>11.82</td></tr><tr><td>Gaia DR2 6015181897983193728<sup>m</sup></td><td>15 51 57.84</td><td>-33 29 33.17</td><td>6.74(0.032)</td><td>-16.22(0.039)</td><td>-22.37(0.026)</td><td>12.03</td></tr><tr><td>Gaia DR2 6014590429442468096<sup>m</sup></td><td>15 45 06.91</td><td>-35 06 21.73</td><td>6.99(0.036)</td><td>-16.97(0.042)</td><td>-23.09(0.029)</td><td>11.82</td></tr><tr><td>Gaia DR2 6009995742152335232<sup>m</sup></td><td>15 44 26.97</td><td>-36 25 42.75</td><td>6.52(0.034)</td><td>-18.30(0.043)</td><td>-23.21(0.031)</td><td>11.82</td></tr><tr><td>Gaia DR2 6011607694917034112<sup>m</sup></td><td>15 50 00.76</td><td>-35 29 19.71</td><td>7.23(0.044)</td><td>-20.18(0.052)</td><td>-25.32(0.034)</td><td>12.37</td></tr><tr><td>Gaia DR2 6011695690208264320<sup>m</sup></td><td>15 47 59.03</td><td>-34 56 38.36</td><td>6.99(0.06)</td><td>-17.93(0.069)</td><td>-25.07(0.045)</td><td>12.69</td></tr><tr><td>Gaia DR2 6011261726715424128</td><td>15 50 29.19</td><td>-36 25 11.80</td><td>6.92(0.11)</td><td>-17.08(0.23)</td><td>-23.52(0.16)</td><td>13.32</td></tr><tr><td>Gaia DR2 6015222957871475584</td><td>15 48 46.12</td><td>-33 18 35.48</td><td>6.69(0.13)</td><td>-19.21(0.26)</td><td>-23.77(0.17)</td><td>13.77</td></tr><tr><td>Gaia DR2 6013030875279571328</td><td>15 41 55.22</td><td>-35 59 35.36</td><td>6.97(0.12)</td><td>-17.12(0.24)</td><td>-25.52(0.14)</td><td>13.17</td></tr><tr><td>Gaia DR2 6014112107523072640<sup>m</sup></td><td>15 34 35.79</td><td>-34 36 01.54</td><td>6.88(0.084)</td><td>-16.89(0.087)</td><td>-24.841(0.066)</td><td>13.14</td></tr><tr><td>Gaia DR2 6012977136650130560<sup>m</sup></td><td>15 39 48.47</td><td>-36 13 48.07</td><td>6.94(0.10)</td><td>-20.069(0.11)</td><td>-23.61(0.069)</td><td>12.81</td></tr><tr><td>Gaia DR2 6015141830223216640</td><td>15 50 19.17</td><td>-33 50 07.12</td><td>6.84(0.15)</td><td>-17.29(0.29)</td><td>-26.46(0.19)</td><td>13.92</td></tr><tr><td>Gaia DR2 6011581856393988352<sup>n</sup></td><td>15 48 06.26</td><td>-35 15 48.15</td><td>6.05(0.07)</td><td>-12.22(0.084)</td><td>-21.04(0.057)</td><td>10.56</td></tr><tr><td>Gaia DR2 6016191485871670400</td><td>15 38 35.63</td><td>-32 02 37.66</td><td>6.53(0.26)</td><td>-18.90(0.39)</td><td>-23.38(0.28)</td><td>14.35</td></tr></tbody></table>

<footnote><sup>a</sup> 2MASS J15464664-3210006 is an M2, T Tauri star (Eisner et al. 2007). <sup>b</sup> aka UCAC4 272-080482, this target is a YSO candidate (Zari et al. 2018). <sup>c</sup> aka UCAC4 279-083370, this target is a YSO candidate (Zari et al. 2018). <sup>d</sup> aka UCAC4 283-086052, this target is a YSO candidate (Zari et al. 2018). <sup>e</sup> aka RX J1557.1-3204A, this target is a YSO candidate (Zari et al. 2018). <sup>f</sup> aka UCAC4 272-081081, this target is a YSO candidate (Zari et al. 2018). <sup>g</sup> aka UCAC4 275-083957, this target is a YSO candidate (Zari et al. 2018). <sup>h</sup> aka UCAC4 282-082547, this target is a YSO candidate (Zari et al. 2018). <sup>i</sup> aka UCAC4 292-084899, this target is a YSO candidate (Zari et al. 2018). <sup>j</sup> aka UCAC4 271-080669, this target is a YSO candidate (Zari et al. 2018). <sup>k</sup> aka UCAC4 274-080590, this target is a YSO candidate (Zari et al. 2018). <sup>l</sup> aka UCAC4 274-080590, this target is a YSO candidate (Zari et al. 2018). <sup>m</sup> This target is a YSO candidate (Zari et al. 2018). <sup>n</sup> aka UCAC4 274-081081, this target is a YSO candidate (Zari et al. 2018).</footnote>
## Appendix B: Age estimation and isochrones

To estimate the age of our targets, we used multiple isochrones for the reasons explained in Sect. 3.2. In this appendix, we present the ages of our targets using various isochrones (Table B.1). We repeat that the ages estimated for all our targets were

overestimated by PARSEC models in comparison with all the other models with a considerable gap. We thus decided to remove the results achieved by the PARSEC models to avoid confusion. This is, however, a well-known problem of PARSEC isochrones that they overestimate the age of cool stars, and all our targets fall in this category.

<table><caption>**Table B.1.** Ages of our targets estimated using various isochrones. The ages are all in millions of years.</caption><thead><tr><th>Name</th><th>Dartmouth std</th><th>Dartmouth mag</th><th>MIST</th><th>Baraffe models</th></tr></thead><tbody><tr><td>2MASS J15383733-3422022</td><td>11</td><td>20</td><td>12.6</td><td>10.7</td></tr><tr><td>Sz 70</td><td>&lt;1</td><td>1</td><td>&lt;0.25</td><td>0.5</td></tr><tr><td>TYC 7335-550-1</td><td>3</td><td>5</td><td>3.5</td><td>3.55</td></tr><tr><td>2MASS J15361110-3444473</td><td>9</td><td>20</td><td>9</td><td>9.77</td></tr><tr><td>2MASS J15523574-3344288</td><td>8</td><td>13</td><td>8</td><td>6.3</td></tr><tr><td>2MASS J15551027-3455045</td><td>-</td><td>-</td><td>-<sup>a</sup></td><td>1.7</td></tr><tr><td>2MASS J16011870-3437332</td><td>9.5</td><td>14</td><td>9.5</td><td>9.55</td></tr><tr><td>UCAC4 269-083981</td><td>4.5</td><td>8</td><td>3.5</td><td>4.2</td></tr><tr><td>Gaia DR2 6010590577947703936</td><td>8</td><td>14</td><td>8</td><td>8.8</td></tr><tr><td>2MASS J15414827-3501458</td><td>2.5</td><td>3</td><td>1.78</td><td>1.82</td></tr><tr><td>UCAC4 273-083363</td><td>4.5</td><td>8</td><td>3.5</td><td>3.63</td></tr><tr><td>Gaia DR2 6014269268967059840</td><td>8</td><td>13</td><td>8</td><td>6.46</td></tr></tbody></table>

## Appendix C: 2MASS J15361110-3444473

The star 2MASS J15361110-3444473 is an M5.5 star according to its VIS spectrum (as we quantitatively indicated) and an M8 star based on its NIR spectrum (based on the fitting done with the BT-Settl model $T_{eff}$ = 2500 K and $log g$ = 4.5, as exhibited in Fig. C.1), with a total extinction of $A_V$ = 1.75 mag. All the spectral typing and analysis that we have performed in this paper are

based on the VIS spectrum of this target; the ROTFIT results especially are all based on the VIS spectrum. Hence, although we keep our analysis limited to the spectroscopy conducted on the VIS spectrum, we would like to emphasize that the possibility of this target being an unresolved binary (composed of two M dwarfs) with SpTs of M5.5 and M8 is viable. Considering the available data, we also cannot rule out the possibility that the star is heavily spotted instead of being a binary.

<figure><img src="image_14.png" /><figcaption>**Fig. C.1.** Flux-calibrated, extinction-corrected NIR spectrum of 2MASS J15361110-3444473 (in black) with its BT-Settl model ($T_{eff}$ = 2500 K and $log g$ = 4.5, in grey).</figcaption></figure>

<footnote><sup>a</sup>None of the three isochrones used here were able to reproduce the stellar parameters of this target due to its dimness.</footnote>
## Appendix B: Age estimation and isochrones

To estimate the age of our targets, we used multiple isochrones for the reasons explained in Sect. 3.2. In this appendix, we present the ages of our targets using various isochrones (Table B.1). We repeat that the ages estimated for all our targets were

overestimated by PARSEC models in comparison with all the other models with a considerable gap. We thus decided to remove the results achieved by the PARSEC models to avoid confusion. This is, however, a well-known problem of PARSEC isochrones that they overestimate the age of cool stars, and all our targets fall in this category.

<table><caption>**Table B.1.** Ages of our targets estimated using various isochrones. The ages are all in millions of years.</caption><thead><tr><th>Name</th><th>Dartmouth std</th><th>Dartmouth mag</th><th>MIST</th><th>Baraffe models</th></tr></thead><tbody><tr><td>2MASS J15383733-3422022</td><td>11</td><td>20</td><td>12.6</td><td>10.7</td></tr><tr><td>Sz 70</td><td>&lt;1</td><td>1</td><td>&lt;0.25</td><td>0.5</td></tr><tr><td>TYC 7335-550-1</td><td>3</td><td>5</td><td>3.5</td><td>3.55</td></tr><tr><td>2MASS J15361110-3444473</td><td>9</td><td>20</td><td>9</td><td>9.77</td></tr><tr><td>2MASS J15523574-3344288</td><td>8</td><td>13</td><td>8</td><td>6.3</td></tr><tr><td>2MASS J15551027-3455045</td><td>-</td><td>-</td><td>-<sup>a</sup></td><td>1.7</td></tr><tr><td>2MASS J16011870-3437332</td><td>9.5</td><td>14</td><td>9.5</td><td>9.55</td></tr><tr><td>UCAC4 269-083981</td><td>4.5</td><td>8</td><td>3.5</td><td>4.2</td></tr><tr><td>Gaia DR2 6010590577947703936</td><td>8</td><td>14</td><td>8</td><td>8.8</td></tr><tr><td>2MASS J15414827-3501458</td><td>2.5</td><td>3</td><td>1.78</td><td>1.82</td></tr><tr><td>UCAC4 273-083363</td><td>4.5</td><td>8</td><td>3.5</td><td>3.63</td></tr><tr><td>Gaia DR2 6014269268967059840</td><td>8</td><td>13</td><td>8</td><td>6.46</td></tr></tbody></table>

## Appendix C: 2MASS J15361110-3444473

The star 2MASS J15361110-3444473 is an M5.5 star according to its VIS spectrum (as we quantitatively indicated) and an M8 star based on its NIR spectrum (based on the fitting done with the BT-Settl model $T_{eff}$ = 2500 K and $log g$ = 4.5, as exhibited in Fig. C.1), with a total extinction of $A_V$ = 1.75 mag. All the spectral typing and analysis that we have performed in this paper are

based on the VIS spectrum of this target; the ROTFIT results especially are all based on the VIS spectrum. Hence, although we keep our analysis limited to the spectroscopy conducted on the VIS spectrum, we would like to emphasize that the possibility of this target being an unresolved binary (composed of two M dwarfs) with SpTs of M5.5 and M8 is viable. Considering the available data, we also cannot rule out the possibility that the star is heavily spotted instead of being a binary.

<figure><img src="image_14.png" /><figcaption>**Fig. C.1.** Flux-calibrated, extinction-corrected NIR spectrum of 2MASS J15361110-3444473 (in black) with its BT-Settl model ($T_{eff}$ = 2500 K and $log g$ = 4.5, in grey).</figcaption></figure>

<footnote><sup>a</sup>None of the three isochrones used here were able to reproduce the stellar parameters of this target due to its dimness.</footnote>
**Appendix D: Updates with Gaia DR3**

As stated in Sect. 2, we used the Gaia DR2 catalog to select our targets. Very recently, Gaia DR3 (Gaia Collaboration 2021) became public and gave us the opportunity to check the catalog for any possible changes or updates on the kinematic or stellar properties of our objects analyzed in this work. We did not find any considerable difference between the kinematic properties reported in both catalogs. However, we report the highlights of our search using these two catalogs in the following paragraphs.

As found in this work, for TYC 7335-550-1 we obtained $T_{eff} = 4488$ K, while in both Gaia DR2 and Gaia DR3 its reported temperature is 5000 K. The reported RV for TYC 7335-550-1 in Gaia DR2 is $1.20 \pm 1.65 \text{ km s}^{-1}$, which is better constrained than the RV we report here ($2.6 \pm 2.0 \text{ km s}^{-1}$). With regard to the wide companion candidate of 2MASS J15361110-3444473, we recalculated their $\Delta v$ using the Gaia DR3 kinematic properties of TYC 7335-550-1, and it resulted in $\Delta v = 5.34 \pm 3.30 (\text{km s}^{-1})$,

which is consistent with the previous $\Delta v = 4.72 \pm 3.47 (\text{km s}^{-1})$. For both of these calculations, we use the RVs calculated by ROTFIT.

The star Sz 70 has a high RUWE in both catalogs (4.86), but we saw no signs of binarity in the spectrum of Sz 70. Using the kinematic properties of Sz 70 reported in Gaia DR3 and those of Sz 71 (which is also updated in Gaia DR3), we recalculated their maximum velocity difference, and it resulted in $\Delta v = 8.36 \pm 3.24 (\text{km s}^{-1})$, which is consistent with the $\Delta v = 6.07 \pm 3.24 (\text{km s}^{-1})$ calculated based on Gaia DR2.

The star 2MASS J15414827-3501458 has a high RUWE (4.198) in both Gaia DR2 and Gaia DR3 catalogs, but we detected no signs of binarity in the spectrum of the object. We report that the kinematic properties of all our targets (parallax and proper motions) are consistent within $3\sigma$ in the two catalogs. Also according to Manara et al. (2022), we do not expect the stellar physical parameters of our core sample to be changed with the astrometry reported in Gaia DR3.
**Appendix D: Updates with Gaia DR3**

As stated in Sect. 2, we used the Gaia DR2 catalog to select our targets. Very recently, Gaia DR3 (Gaia Collaboration 2021) became public and gave us the opportunity to check the catalog for any possible changes or updates on the kinematic or stellar properties of our objects analyzed in this work. We did not find any considerable difference between the kinematic properties reported in both catalogs. However, we report the highlights of our search using these two catalogs in the following paragraphs.

As found in this work, for TYC 7335-550-1 we obtained $T_{eff} = 4488$ K, while in both Gaia DR2 and Gaia DR3 its reported temperature is 5000 K. The reported RV for TYC 7335-550-1 in Gaia DR2 is $1.20 \pm 1.65 \text{ km s}^{-1}$, which is better constrained than the RV we report here ($2.6 \pm 2.0 \text{ km s}^{-1}$). With regard to the wide companion candidate of 2MASS J15361110-3444473, we recalculated their $\Delta v$ using the Gaia DR3 kinematic properties of TYC 7335-550-1, and it resulted in $\Delta v = 5.34 \pm 3.30 (\text{km s}^{-1})$,

which is consistent with the previous $\Delta v = 4.72 \pm 3.47 (\text{km s}^{-1})$. For both of these calculations, we use the RVs calculated by ROTFIT.

The star Sz 70 has a high RUWE in both catalogs (4.86), but we saw no signs of binarity in the spectrum of Sz 70. Using the kinematic properties of Sz 70 reported in Gaia DR3 and those of Sz 71 (which is also updated in Gaia DR3), we recalculated their maximum velocity difference, and it resulted in $\Delta v = 8.36 \pm 3.24 (\text{km s}^{-1})$, which is consistent with the $\Delta v = 6.07 \pm 3.24 (\text{km s}^{-1})$ calculated based on Gaia DR2.

The star 2MASS J15414827-3501458 has a high RUWE (4.198) in both Gaia DR2 and Gaia DR3 catalogs, but we detected no signs of binarity in the spectrum of the object. We report that the kinematic properties of all our targets (parallax and proper motions) are consistent within $3\sigma$ in the two catalogs. Also according to Manara et al. (2022), we do not expect the stellar physical parameters of our core sample to be changed with the astrometry reported in Gaia DR3.