- Press Release
- Oct 2, 2022
NASA Hubble Space Telescope Daily Report #5123
HUBBLE SPACE TELESCOPE DAILY REPORT #5123
Continuing to Collect World Class Science
PERIOD COVERED: 5am June 22 – 5am June 23, 2010 (DOY 173/09:00z-174/09:00z)
FLIGHT OPERATIONS SUMMARY:
Significant Spacecraft Anomalies: (The following are preliminary reports of potential non-nominal performance that will be investigated.)
12310 – GSAcq(2,1,1) scheduled at 173/21:05:45z and REAcq scheduled at 173/22:00:26z both resulted in fine lock backup (2,0,2).
Observations possibly affected: STIS 23 – 27 Proposal ID#11693; STIS 28 &29 Proposal ID#11857
COMPLETED OPS REQUEST: (None)
COMPLETED OPS NOTES: (None)
FGS GSAcq 5 5
FGS REAcq 4 4
OBAD with Maneuver 4 4
SIGNIFICANT EVENTS: (None)
Definitive ISM Abundances through Low-mass X-ray Binaries as Lighthouses
We propose observations of the UV spectra of two low-mass X-ray binaries (Sco X-1 and Cyg X-2) with existing Chandra X-Ray Observatory (CXO) data. From the X-ray data we will measure total (phase-independent) column densities of O, Ne, and Fe. From the UV data we will determine gas-phase column densities of H and O. The data in conjunction will allow us to make unique measurements of the total interstellar abundances of oxygen, neon, and iron, and direct measurements of the dust-phase abundances of O and Fe.
Beyond the Classical Paradigm of Stellar Winds: Investigating Clumping, Rotation and the Weak Wind Problem in SMC O Stars
SMC O stars provide an unrivaled opportunity to probe star formation, evolution, and the feedback of massive stars in an environment similar to the epoch of the peak in star formation history. Two recent breakthroughs in the study of hot, massive stars have important consequences for understanding the chemical enrichment and buildup of stellar mass in the Universe. The first is the realization that rotation plays a major role in influencing the evolution of massive stars and their feedback on the surrounding environment. The second is a drastic downward revision of the mass loss rates of massive stars coming from an improved description of their winds. STIS spectroscopy of SMC O stars combined with state-of-the-art NLTE analyses has shed new light on these two topics. A majority of SMC O stars reveal CNO- cycle processed material brought at their surface by rotational mixing. Secondly, the FUV wind lines of early O stars provide strong indications of the clumped nature of their wind. Moreover, we first drew attention to some late-O dwarfs showing extremely weak wind signatures. Consequently, we have derived mass loss rates from STIS spectroscopy that are significantly lower than the current theoretical predictions used in evolutionary models. Because of the limited size of the current sample (and some clear bias toward stars with sharp-lined spectra), these results must however be viewed as tentative. Thanks to the high efficiency of COS in the FUV range, we propose now to obtain high-resolution FUV spectra with COS of a larger sample of SMC O stars to study systematically rotation and wind properties of massive stars at low metallicity. The analysis of the FUV wind lines will be based on our 2D extension of CMFGEN to model axi-symmetric rotating winds.
An Astrometric Calibration of Population II Distance Indicators
In 2002, HST produced a highly precise parallax for RR Lyrae. That measurement resulted in an absolute magnitude, M(V)= 0.61+/-0.11, a useful result, judged by the over ten refereed citations each year since. It is, however, unsatisfactory to have the direct, parallax-based, distance scale of Population II variables based on a single star. We propose, therefore, to obtain the parallaxes of four additional RR Lyrae stars and two Population II Cepheids, or W Vir stars. The Population II Cepheids lie with the RR Lyrae stars on a common K-band Period-Luminosity relation. Using these parallaxes to inform that relationship, we anticipate a zero point error of 0.04 magnitude. This result should greatly strengthen confidence in the Population II distance scale and increase our understanding of RR Lyrae star and Pop. II Cepheid astrophysics.
Follow-up Observations of Debris Disks around Two Solar-Type Stars
Circumstellar debris disks offer direct views into the structure of extrasolar planetary systems. Their constituent dust, seen in scattered light and thermal emission, is created by the collisions of asteroidal and cometary parent bodies. The distribution of this dust provides information on the location of the parent bodies, and can be strongly affected by planetary perturbations. Dynamical signatures of planets can include asymmetries, warps, central clearings, and radial gaps in a disk, and thus are key features to search for in resolved images. Following up recent Spitzer measurements, we have now detected two new, nearby debris disks in scattered light. Our initial ACS F606W coronagraphic images show faint ringlike structures around the solar-type stars HD 10647 (F9V) and HD 207129 (G0V); both are also spatially resolved in Spitzer/MIPS 70 micron images. The HD 10647 disk, seen close to edge-on, represents the first disk ever imaged in scattered light around a star known to have a radial velocity planet. The inclined ring around HD 207129 is the faintest disk ever imaged in scattered light, and seems in the MIPS image to be asymmetric like the eccentric ring around Fomalhaut. We propose to obtain deep ACS coronagraphic images of these two disks. Our goals are to get definitive measurements of the dust spatial distributions (including disk asymmetries and sharpness of the ring edges), and measure the overall F606W-F814W color of each disk in order to constrain the dust properties. The results will be a definitive exploration of the Kuiper belts of two nearby, Sun-like stars. NOTE: HD 207129 was deleted from this program.
CCD Dark Monitor Part 2
Monitor the darks for the STIS CCD.
CCD Bias Monitor-Part 2
Monitor the bias in the 1×1, 1×2, 2×1, and 2×2 bin settings at gain=1, and 1×1 at gain = 4, to build up high-S/N superbiases and track the evolution of hot columns.
Boron Abundances in Rapidly Rotating Early-B Stars
Models of rotation in early-B stars predict that rotationally driven mixing should deplete surface boron abundances during the main-sequence lifetime of many stars. However, recent work has shown that many boron depleted stars are intrinsically slow rotators for which models predict no depletion should have occurred, while observations of nitrogen in some more rapidly rotating stars show less mixing than the models predict. Boron can provide unique information on the earliest stages of mixing in B stars, but previous surveys have been biased towards narrow- lined stars because of the difficulty in measuring boron abundances in rapidly rotating stars. The two targets observed as part of our Cycle 13 SNAP program 10175, just before STIS failed, demonstrate that it is possible to make useful boron abundance measurements for early-B stars with Vsin(i) above 100 km/s. We propose to extend that survey to a large enough sample of stars to allow statistically significant tests of models of rotational mixing in early-B stars.
STIS Cycle 17 MAMA Dark Monitor
This proposal monitors the behavior of the dark current in each of the MAMA detectors.
The basic monitor takes two 1380s ACCUM darks each week with each detector. However, starting Oct 5, pairs are only included for weeks that the LRP has external MAMA observations planned. The weekly pairs of exposures for each detector are linked so that they are taken at opposite ends of the same SAA free interval. This pairing of exposures will make it easier to separate long and short term temporal variability from temperature dependent changes.
For both detectors, additional blocks of exposures are taken once every six months. These are groups of five 1314s FUV-MAMA Time-Tag darks or five 3x315s NUV ACCUM darks distributed over a single SAA-free interval. This will give more information on the brightness of the FUV MAMA dark current as a function of the amount of time that the HV has been on, and for the NUV MAMA will give a better measure of the short term temperature dependence.
IR Dark Current Monitor
Analyses of ground test data showed that dark current signals are more reliably removed from science data using darks taken with the same exposure sequences as the science data, than with a single dark current image scaled by desired exposure time. Therefore, dark current images must be collected using all sample sequences that will be used in science observations. These observations will be used to monitor changes in the dark current of the WFC3-IR channel on a day-to-day basis, and to build calibration dark current ramps for each of the sample sequences to be used by Gos in Cycle 17. For each sample sequence/array size combination, a median ramp will be created and delivered to the calibration database system (CDBS).
WFC3 UVIS CCD Daily Monitor
The behavior of the WFC3 UVIS CCD will be monitored daily with a set of full-frame, four-amp bias and dark frames. A smaller set of 2Kx4K subarray biases are acquired at less frequent intervals throughout the cycle to support subarray science observations. The internals from this proposal, along with those from the anneal procedure (Proposal 11909), will be used to generate the necessary superbias and superdark reference files for the calibration pipeline (CDBS).
Cycle 17: UVIS Bowtie Monitor
Ground testing revealed an intermittent hysteresis type effect in the UVIS detector (both CCDs) at the level of ~1%, lasting hours to days. Initially found via an unexpected bowtie-shaped feature in flatfield ratios, subsequent lab tests on similar e2v devices have since shown that it is also present as simply an overall offset across the entire CCD, i.e., a QE offset without any discernable pattern. These lab tests have further revealed that overexposing the detector to count levels several times full well fills the traps and effectively neutralizes the bowtie. Each visit in this proposal acquires a set of three 3×3 binned internal flatfields: the first unsaturated image will be used to detect any bowtie, the second, highly exposed image will neutralize the bowtie if it is present, and the final image will allow for verification that the bowtie is gone.
UVIS Hot Pixel Anneal
The on-orbit radiation environment of WFC3 will continually generate new hot pixels. This proposal performs the procedure required for repairing those hot pixels in the UVIS CCDs. During an anneal, the two-stage thermo-electric cooler (TEC) is turned off and the four-stage TEC is used as a heater to bring the UVIS CCDs up to ~20 deg. C. As a result of the CCD warmup, a majority of the hot pixels will be fixed; previous instruments such as WFPC2 and ACS have seen repair rates of about 80%. Internal UVIS exposures are taken before and after each anneal, to allow an assessment of the procedure’s effectiveness in WFC3, provide a check of bias, global dark current, and hot pixel levels, as well as support hysteresis (bowtie) monitoring and CDBS reference file generation. One IR dark is taken after each anneal, to provide a check of the IR detector.