# Presentation: 161395

## SWIFT/UVOT Observations 

**of SNe Ia**
- Peter A. Milne (Steward Observatory)
- on behalf of SWIFT SN Ia Team

- SN 2005ke (Ia)

## Utility of UV & X-ray Observations

- 1) **Explosion Physics**. UV affords another window into SN physics.
- - iron-peak line blanketing occurs in UV. Early epochs probe iron near the surface
- - absorption of UV leads to more emission in optical....which must be modeled properly in order to acceptably fit entire spectrum.
- - YOUNG SNe preferred to study distribution of iron-peak elements
- 2) **CSM(Progenitor/Donor Star/Mass Transfer)**. X-ray emission from shocked CSM might extend down to UV wavelengths.
- 3) **Cosmology**. With increasing redshift, rest-frame UV emission shifted into optical. Thus, UV observations of nearby SNe Ia permit the creation of templates against which high-z observations can be compared, _if UV peaks magnitudes largely homogeneous_.

## HST & IUE Spectral Studies of SNe Ia

- SN 1981B (IUE), 1990N (IUE), 1992A (HST-FOS) first studied.

- Pauldrach (from Kirshner et al. 1993.....D.Jeffery worked on this)

- A series of spectra and F275W photometry was obtained for 1992A.

## HST & IUE Spectral Studies of SNe Ia

- SNe 2004dt, 2004ef, 2005M observed in Cycle 14 (also some Cycle 9).

- Wang et al. 2005

**2004dt**
**(post-peak)**

- UV clearly a wavelength region of dramatic flux variation.

## Swift: UVOT & XRT

-  Swift is a GRB-finder mission.
-  UVOT & XRT search for counterparts of BAT-detected GRBs.
-  GRBs isotropic - observing SNe does not degrade the primary science mission.

-  SN observing scheduled very quickly after SN discovery (hours-days), provided there are no GRB follow-ups or other conflicts (comets, etc.). Faster than HST or other potential UV telescopes.
-  A 90 degree Sun-angle criterion has been added to avoid detecting GRBs too near the Sun for ground-based follow-up.
-  Swift can continually monitor the SNe for months, with exposure times that are impossible with other missions (complete light curves)

## UVOT

-  30 cm telescope
-  ugrism & vgrism, but most results to date from photometry.
-  U,B,V & UVW1,UVM2, UVW2
-  photon counter, so coincidence a problem for V < 13.5m

-  B & V band photometry have been compared with ground-based photometry (Li et al. 2005). Zero points & optimal aperture
-  One SN observed with both HST & UVOT (2005cf) - analysis in progress (Li et al. in prep.)

## Sample: 10 SNe Ia..........so far

- 05am - slightly sublum (1.69)
- 05cf - slightly superlum (1.06)
- 05df - ANU ~normal (1.1)
- 05hk - anomalous (02cx-like, 1.56)
- 05ke - very sublum (1.84)
- 06X - slightly SUPERLUM
- ***
- 06dd - missed peak (1.31)
- 06dm - slightly sublum (1.42)
- 06ej - post-peak (1.16)
- ***
- 07S - 91T-like?

** ****Optical light curves important to place SN in continuum of SN Ia events.**** **

## SN 2005cf - KAIT

** ****Optical light curves important to place SN in continuum of SN Ia events.**** **

**2005cf - KAIT-B**

## SNe Ia -Optical (ground-based): 2005hk & 2005ke

- 05am - CSP, SLOTIS
- 05cf - KAIT, CSP, slotis
- 05df - ANU
- 05hk - KAIT, SLOTIS, CSP
- 05ke - SLOTIS, CSP
- 06X - KAIT, SLOTIS,

**CSP**

- CSP

## Five SNe Ia -UVOT                        ~F275W 

-  These comparisons do not require knowing distance & extinction.

## Five SNe Ia -UVOT                      UVW1  & W2

-  These comparisons do not require knowing distance & extinction.

## SN 2005am: 

**SN 2005am: **
**UVW1 vs U & B**

## SN 2005cf: 

**UVW1 vs U & B**

## SN 2005df: 

**UVW1 vs U & B**

## SN 2005ke: 

**UVW1 vs U & B**

## Point #1:

**The UV light curves have similar shapes. **
** ****The light curves appear more homogeneous than the optical light curves.**
** ****Curves were shifted in time & magnitude to fit templates. **

## UVW2: Consistent with UVW1

## Mean Template: 

**UVW1**

-  Assumes all UVW1 light curves have the same shape.
- Individual light curves iteratively fit to template.
-  Improves the peak date & magnitude determination.

## Template versus optical

## Point #2:

**The UV mean template rises slightly quicker and fades slightly slower relative to U-band normal template. **

## UV versus Optical Light Curves (peak dates)

-  Rough tracer of iron-peak elements near surface.

-    UVW1
-    UVW2
- * UVM2

## Point #3:

**The UV light curves peak at roughly the same date as the B-band. **
**The exceptions are the SNe Ia for which iron-peak elements are detected in the early-epoch spectra. **

## Standard Candle Study

-  One important investigation is determining whether the UV light curves might be useful as cosmological distance indicators.
-  The template fitting permits determination of the peak apparent magnitude. The Lira relation and/or MLCS2k2 fitting and or polarization studies permit estimation of the extinction.
-  The distance can be estimated by redshift, by assuming the LWR or by independent distance estimates.

## UV Light Curves as Standard Candles

- Brown et al., in prep.

## The Luminosity-Width relation

## UV Light Curves as Standard Candles

- Brown et al., in prep.

## UV Light Curves as Standard Candles

- Brown et al., in prep.

## Point #4:

**SNe Ia that are optically bright at peak are also brighter in the UV at peak. **

## SN 2005ke - Late Epochs

-  UV excess starting 12-15 days post-peak!

- Immler et al. 2006

## SN 2005ke - Late Epochs    UVW1 & UVW2

-  UV excess starting 12-15 days post-peak!

## SN 2005ke - Late Epochs

-  Is this emission from shocked CSM? If so, why no optical signature as was observed in the H-alpha emission from SN 2002ic?
-  2002ic fitted with CSM component that contributed at roughly peak light. For 2005ke....emission later (spatially farther inner edge?). 2002ic suggested AGB star mass loss
-  Mass loss rate consistent with giant branch star < 10 SM....model depend.
-  Chandra observed around 80 days....no detection. But factor 4-5 fainter.

- Immler et al. 2006

## SN 2005ke - Late Epochs

-  Dashed lines - 91bg, open diamonds - 99by..........**NO EXCESS!!**

- SLOTIS

## Point #5:

**SN 2005ke exhibited UV and X-ray emission that is likely due to the shock reaching CSM surrounding the SN.**
** ****Although the significance of the XRT detection is low, there is a temporal correlation with an excess in the UVW1 and UVW2 filters. **
** ****The SN was detected to a much lower magnitude at early and late epochs....arguing against host galaxy contamination being important. **

## Projects in the works:

_**Bolometric/SED**_** - Generating UV-OPT-NIR bolometric light curves & SED evolution. **
_**Extinction**_** - SN 2006X & 2006mr were detected through very high extinction. This will allow the study of the wavelength dependence of extinction in the UV energy range. **
_**Late Light Curves**_** - Image subtraction will permit the SNe to be monitored to later epochs than ever before (100-200days?). **

## Summary 

- UVOT and XRT are observing SNe Ia, starting at early epochs and monitoring the SNe to 100+ days.
-  Early-epoch UV photometry probes the iron-peak elements near the surface of the ejecta.
-  When combined with Optical & NIR observations, these will produce wide multi-wavelength campaigns on SNe Ia.
-  More SNe will be observed, allowing observations of different varieties of SNe Ia, as well as observing multiple optically-similar SNe Ia.
-  Estimating the distances and extinction to these SNe will permit the determination of the absolute UV magnitudes of these SNe....and determination  of whether they can be treated as standard candles.
-  The sublum SN 2005ke exhibited CSM emission, will others?

## SN 2005am - a 92A-like SN